The use of surgical fixation plates for a variety of orthopedic applications is widely accepted. The plates are used by surgeons to stabilize, mend, or align a patient's bone as well as alter compression of patient's bones, and are typically fastened to the bones with a plurality of fasteners, such as, screws that are installed through holes in the plate. Proper orientation and alignment of fasteners and secure surgical fixation of the plate can mitigate some of the potential complications after implantation.
Locking bone plates used in spinal applications must be installed with special care, as the plates may be used for long term, intravertebral fixation, bone-fragment fixation, and anterior decompression of vertebra of the spine. The margin for error in spinal surgery is small, particularly because of the sensitivity of the spinal cord and the risk inherent with invasive procedures around the spinal cord. Furthermore, the dimensions of vertebral bone available for setting fasteners are fairly constrained.
Screws, used to secure the plate to the bone, should be properly aligned with the associated fixation plate hole so that each screw is seated correctly within the plate. Any misalignment of the screw within the plate hole risks tissue damage. In addition, improperly seated screws may result in an unstable or insecure connection of the plate to the bony material, thus potentially defeating the usefulness of the plate. Locking plates, in particular, demand precise fastener alignment.
Drill guides are often used to assist the surgeon in aligning the screws with the plate holes. Drill guides for locking plates attach or abut to the plate and generally include a guide tube for guiding a drill bit. One drawback of traditional drill guides is that the drill guides do not provide adequate soft tissue protection. This is of particular concern when the surgeon is installing the plate using an anterior approach to the spine through the abdomen or chest region. Many sensitive and vital organs reside in the chest and abdomen and a surgeon must be especially careful not to damage these organs when operating on the spine. Thus, the surgeon must proceed with caution, requiring more time for the procedure and thus increasing the chance of complications for the patient under anesthesia.
Another drawback of conventional drill guides is that they do not engage the plate in a manner that prevents lateral or rotational movement of the plate with respect to the drill guide.